Noise suppression apparatus and systems are vital in many fields, most notably in the development and ground testing of aircraft engines. The U.S. Air Force alone has noise suppression apparatus worth at least 250 million dollars and related real property worth at least 60 million dollars. Modern noise suppression apparatus—typically large and fixed—must regularly be maintained, upgraded, and overhauled in the field. Experience in the art has soundly demonstrated that improper or inadequate installation and/or insufficient maintenance of a noise suppressor and the like can cause significant damage to noise suppression systems, per se, and, of course, to implicated engines and aircraft. Indeed, improper or inadequate installation and/or insufficient maintenance of a noise suppressor can even cause permanent injury and loss of life.
Noise or sound suppression methodology has existed in the prior art for more than 20 years and commonly includes a sound augmenter cavity filled with a bottom layer of loose basalt covered by a basalt blanket. This basalt blanket is, in turn, wrapped with a wire mesh screen that encapsulates the insulation. This augmenter cavity is sealed with a stainless steel liner sheet and perforated to allow the transfer of sound and heat. It will be readily appreciated that, while such sound suppression technology has substantially remained stagnant, aircraft engines have continuously been improved, thereby concomitantly creating more noise. These developments in the art have adversely affected pre-existing noise suppression systems wherein modern aircraft engines not only have inherently stronger aerodynamics, but also engender intensified shock and thermal forces.
The common use of a fixed quantity of loose basalt often effects consequent settling thereof, which inevitably causes the sound augmenter and deflector cavities to be only partially filled therewith. Exhaust gases generated during engine operation create aerodynamic turbulence in the sound attenuation system, wherein engine thrust generates shock waves that are transferred to the noise suppressor structure. The high-temperature exhaust gases also transfer a large thermodynamic load to the sound suppression system. Since the prior art fails to densely pack augmenter cavities with basalt and simultaneously fails to stabilize the basalt, the prevalence of aerodynamic turbulence causes the tumbling of components therewithin. This, unfortunately, has been observed to cause basalt fibers to break down and to be inadvertently be expelled therefrom. This significant loss of insulation effects subsequent loss of thermal insulating capacity, loss of mass absorption capability against shock waves, and loss of acoustical attenuation capacity. This lowered noise suppression capability, in the face of aerodynamic and thermodynamic forces, causes these forces to be exerted on the sound suppression structure, per se, and thereby cause damage to or possibly even destroy expensive components. Indeed, such deficient noise suppression infrastructure tends to negate any sound attenuation capability thereof. It should be evident that such deficiencies and vulnerabilities of conventional noise suppression systems defeat its raison d'etre.
It will be appreciated that noise suppression systems known in the art must be maintained and repaired every one to five years, normally via replacement of lost or degraded insulating material, and concomitant repair of damaged structural components. It is also common knowledge among practitioners in the art that repetitive and frequent re-packing of sound augmenter and deflector insulation material tends to effectuate frequent facility down-times, to disrupt pre-planned facility activities, and consequently to increase costs attributable to necessary scheduling of frequent maintenance procedures. It will be readily appreciated that this crucial maintenance necessarily depends upon shipping of essential parts and materials.
It will also be understood that failing to rigorously maintain conventional noise suppression apparatus can cause sub-optimal sound attenuation which might cause personnel to suffer serious bodily injury, permanent disability, and even death. Improperly maintained components of a sound attenuation system contemplated hereunder are susceptible to damage from both aerodynamic and thermodynamic forces. Additionally, aircraft engines or aircraft, per se, in the process of being tested, can similarly be damaged or destroyed as a result of improper maintenance regimen which can, in turn, effect degradation and outright loss of insulation.
It is also known by those skilled in the art that basalt varies in density, form, and chemical composition. Indeed, it will be appreciated that not all basalt is suited to be used as insulating mineral wool or the like. The chemical composition of basalt fibers is directly related to insulation performance under various temperature conditions, applied forces, and metallic contact both within a noise attenuation apparatus and within the atmosphere at large. Basalt that has not been carefully selected based upon suitable prerequisite chemical composition may degrade readily under extreme conditions including high temperature, high pressure, and/or contact with systemic or atmospheric metals.
Field experience indicates that augmenters which have been in service for fewer than five years suffer from 85-90% depletion of insulation. This insulation depletion phenomenon has been observed to effect extensive internal structural damage associated with thermal heat transfers and vibratory loading that have been found to be attributable to inadequate insulation-packing. In particular, this damage can cause paint on interior surfaces to become abraded due to internal movement of fill materials and implicated wire screen during jet engine testing; it can also cause extensive wear to structural members at elongated slots, eventually leading to corrosion of metallic structural components. It is also known that inadequate installation also contributes to internal component damage.
For instance, interior compartment damage has been attributed to failure to secure floating bars, in situ, at structural slot locations, at improper stud weldments, and at broken welds affixed upon floating bar assemblies of structural slots. Bags of basalt insulation are commonly found to be installed in wrapping and matts, but not in wire screens. Furthermore, batten bars and other metallic materials have frequently been found to be inflicted with heavy corrosion.
Frequent demands that have been made and continue to be made—pertinent to re-packing of noise augmenters and deflectors—have been unable to keep abreast of apace developments of larger and more powerful jet engines and the like. It is not uncommon, unfortunately, to continue field operations of poorly maintained, sub-optimally performing augmenters and deflectors. Hence, it is a long-standing disability of the prior art that frequent failures persist because of a paucity of insight how to address the nature and scope of this noise-suppression problem. It should be evident that such insight is crucial in the context of hush house design, including not only manufacture and supply, but also, maintenance and repair thereof.
To avoid this downside of insulation loss, practitioners have adopted the methodology of frequently and repetitively re-packing augmenters and deflectors. Otherwise, it is well established that facilities will suffer unavoidable downtime which clearly has a detrimental impact upon jet engine efficiency and mission capabilities; increased costs attributable to engine shop work-arounds; the necessity for more shipments and deliveries of parts and the like due to frequent maintenance. Obviously, this frequent re-packing protocol drives life-cycle costs to unanticipated painfully-higher levels.
For instance, presently-known augmenter systems, as hereinbefore described, typically comprise a bottom layer of loose basalt blanketed by a single basalt layer which is, in turn, wrapped with a wire-mesh screening that is tucked around the basalt insulation layers. The top of the augmenter cavity is sealed by a stainless steel liner sheet that is perforated to enable both thermal and sound insulation. Packing the augmenter according to procedures known in the art requires a predetermined number of basalt bags—of particular weight and density—to be installed per augmenter cavity. As is known by those skilled in the art, this packing protocol only partially fills augmenter cavities.
It is well known that basalt rock varies by type that devolves from a certain chemical composition that determines its applicability for use as road base, rock or mineral wool, or for use in fiber manufacture. It should be noted that fiber properties including chemical composition has a substantial impact upon performance under exigent conditions typified by vibration, heat, and both metallic-contact and atmospheric-contact.
It is also known that exhaust gases generated during engine tests and the like create aerodynamic turbulence when a mixture of cooling air and engine exhaust exit through the engine exhaust system. As will be understood by those skilled in the art, engine thrust generates significant shock waves which are transferred to the noise suppressor foundation and related structures. These gases exit at high temperatures consequently transferring significant thermodynamic load to the exhaust system.
An inherent deficiency of this conventional exhaust system is that aerodynamic turbulence is transferred into the augmenter cavity. As hereinbefore described, this turbulence-transfer is due to the augmenter cavity not being thoroughly and tightly packed with basalt—with the basalt not being stabilized. It has been observed that turbulence causes the wire-mesh blanket and loose basalt to be dispersed throughout the augmenter cavity. It is also known that, making an adverse situation even worse, basalt fibers originally packed within this augmenter cavity are caused to break down by intense vibration and tumbling engendered during jet engine testing. It will be appreciated that these degraded basalt fibers are subsequently apt to be blown out of the augmenter cavity and deflector panels. Unfortunately, this degradation may be exacerbated by particular types of basalt fiber used which has been found to be inextricably intertwined with fiber-source, by temperature rating, and by fiber size (diameter and length).
In spite of these commonly used methods that strive to sustain exhaust system integrity, inherent basalt degradation unavoidably causes diminished thermal insulating capacity and diminished mass absorption capacity for coping with shock waves and effectuating acoustical attenuation. It will be understood by practitioners in the art that metal fatigue and system-component failure typically follow—possibly even to the extent of causing facility shutdown. Under these adverse circumstances, it will be readily appreciated that this plethora of conventional system deficiencies is functionally related to increased costs imposed by the criticality of performing frequent maintenance and repair of a plurality of augmenter internal metal components. Ironically, the loss of acoustical-attenuation capacity, in turn, degrades noise suppressor performance which undermines the very functional purpose of the exhaust system augmenter and associated noise suppression apparatus and procedures.
Field experience has demonstrated that augmenters which have been placed in service for less than five years have insulation situated within the augmenter cavity asymptotically approaching 85-90% depletion. This all-too-common scenario has been frequently documented with concomitant extensive internal structural damage associated with intense thermal heat transfers and vibratory loading. Of course, such internal structural damage may be attributable to inadequate packing. In particular, this damage has been identified to flow from paint-abrasion caused by internal movement of fill materials and wire screen that undermines the integrity of interior structural members during jet engine testing and the like. Internal structural damage has also been identified as flowing from extensive wear of structural members at elongated slots. Furthermore, damage to interior compartments has been attributed to failure at structural slot locations prerequisite for securing floating bars, in situ; to improper stud weldments; and to broken welds that were intended to be affixed to structural slots' floating bar assemblies used to secure the floating bars, per se. It will thus be appreciated that such interior compartment damage signals the onset of corrosion in view of the existence of inadequate protective coating, thereby leading to material deterioration and breakdown.
It has been found that other deficiencies tend to undermine effectiveness and efficiency of sound suppressor systems contemplated hereunder. One such deficiency is routinely including undetermined residual fill material functioning as augmenter packing. This, of course, impacts a plurality of augmenter components: the augmenter section located closest to the collector tube which is designed to protect the collector tube from thermal temperatures and thrust; stainless steel liner panels which are apt to corrode; support members welded to the liner panels which are also apt to corrode.
It should be evident that this corrosion is attributable to insulation loss and resultant exposure to higher temperatures. It has also been observed in the field that workmanship problems are not uncommon. For instance, basalt bags of insulation have been found to be installed in wrapping; and basalt matt and wire screen have been found to be missing outright. In addition, batten material has been found to be heavily corroded.
As will be clear to those conversant in the art that constant protracted exhaust systems failure known in the art is attributable to sound suppression systems lagging behind ongoing jet engine developments. That is, while conventional sound suppression and attenuation system was originally substantially designed in 1979 and was re-designed 1985, engine thrust level has changed significantly during a 1979-1985 time frame.
As should be evident to those skilled in the art, an upgrade program as hereinafter described has not heretofore been contemplated. Inherent in the art, has been and continues to be frequent demand for re-packing of augmenters and deflectors in the field. Moreover, it will also be appreciated that, not-uncommonly, in the art to continue field-operation of poorly-maintained, sub-optimally-performing augmenters and deflectors. Yet another long-standing disability of the prior art is failure of practitioners to have sufficient insight to properly address the nature and scope of this seemingly indigenous problem. Indeed, there appears to be an invisible wall between design, manufacture, and supply of hush houses and the like, on the one hand, and maintenance and repair thereof, on the other hand.
Heretofore, there does not exist an adequate apparatus and an associated systemic method for providing reliable and effective noise augmenter and deflector installation, upgrade, maintenance, and repair. The prior art has been unable to provide specially-selected, cost-effective materials and concomitant structures to assure functionality and longevity of such materials and implicated noise suppression system components. Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided for enabling improved noise suppression apparatus and methodology.